1. Field of the Invention
The present invention relates to an ink jet cartridge for an ink jet recording apparatus wherein image information is recorded by ejecting ink or the like toward a recording medium.
2. Description of the Related Art
Heretofore, an ink jet recording apparatus wherein image information is recorded by ejecting ink or the like toward a recording medium has employed an ink jet cartridge comprising a recording head for forming droplets of the ink ejected toward the recording medium and an ink tank for containing the ink and supplying the ink to the recording head, the recording head and the ink tank being joined together.
FIG. 1 is a cross-sectional view showing the structure of one prior art ink jet cartridge.
As shown in FIG. 1, the prior art ink jet cartridge mainly comprises a recording head 27 from which ink is ejected toward a recording medium (not shown), and an ink tank 20 in which the ink to be ejected from the recording head 27 is stored. The ink tank 20 contains an ink absorbing member 21 for retaining the ink that is impregnated therein. Also, the ink tank 20 has an ink supply port 22 through which the ink retained by the ink absorbing member 21 is supplied to the recording head 27, and an atmosphere communicating port 23 through which the atmosphere outside the ink tank 20 is communicated with the air inside the ink tank 20 to prevent a negative pressure in the tank inner space from rising excessively. Further, as disclosed in Japanese Patent Laid-Open No. 3-101971, the ink tank 20 is provided on its inner wall surfaces with ribs 24 to 26 which serve to distribute the ambient air introduced through the atmosphere communicating port 23 to various portions of the ink absorbing member 21, enabling the ink impregnated in the ink absorbing member 21 to be evenly introduced to the ink supply port 22. In a portion of the rib 24 near the atmosphere communicating port 23, the height of the rib 24 projecting from the inner wall surface of the ink tank 20 is greater than in the other portion of the rib 24 so that the ambient air introduced through the atmosphere communicating port 23 is certainly supplied to the ink absorbing member 21.
In the ink jet cartridge described above, the ink impregnated in the ink absorbing member 21 is supplied to the recording head 27 through the ink supply port 22 by the capillary-attraction depending on consumption of the ink in the recording head 27. The ink is then ejected toward the recording medium from the recording head 27. Corresponding to the amount of the ink consumed, the ambient air is introduced to the ink tank 20 through the atmosphere communicating port 23.
In order to that the ink absorbing member 21 can properly retain the ink therein, the amount of the ink impregnated in the ink absorbing member 21 must be less than the volume of the ink absorbing member 21, while allowing the ink absorbing member 21 to develop the capillary attraction. To this end, a vacant space (a portion A in FIG. 1) where the ink is not impregnated from the beginning necessarily exists in the ink absorbing member 21. No matter where the vacant space exists, the ink absorbing member 21 can sufficiently develop its function of retaining the ink therein. But if the vacant space exists near the ink supply port 22, the ink flow may be blocked to prevent the ink from being supplied to the recording head 27. To avoid that the vacant space where the ink is not impregnated will exist near the ink supply port 22, the ink is poured into the ink tank through the ink supply port 22 in the manufacture process.
The ink poured through the ink supply port 22 flows through the ink absorbing member 21 and reaches the rib 26. Then, the ink passes gaps or guide paths formed by the ribs 26, 25 and 24 and comes to the side near the atmosphere communicating port 23. The ink is thus impregnated in the ink absorbing member 21 while finally leaving a vacant space in the portion A.
Here, the ink absorbing member 21 is inserted in the ink tank 20 in a compressed state.
In the prior art ink jet cartridge described above, however, because a portion of the rib 24 near the atmosphere communicating port 23 projects from the inner wall surface of the ink tank with greater height than in the other portion of the rib 24 so that the ambient air introduced through the atmosphere communicating port 23 is certainly supplied to the ink absorbing member 21, a portion B of the ink absorbing member 21 where it bumps the above higher portion of the rib 24 is brought into a more compressed state than in the other portion of the ink absorbing member 21 when the ink absorbing member 21 is inserted in the ink tank 20 in a compressed state. Therefore, when the ink is poured into the ink tank 20, the ink is impregnated in a more amount in the portion B of the ink absorbing member 21.
In practical use, there occur no problems even with the ink so impregnated in the ink absorbing member. But if the ink jet cartridge is subjected to a thermal impact or a pressure reduced state while it is delivered from the manufacture factory to the user, the air near the portion A expands, whereupon the ink accumulated in the portion B is pushed out to leak into a space where the atmosphere communicating port 23 is located. In the worst case, the leaked ink is forced to exude to the outside of the ink jet cartridge, resulting in a feat that the user""s hands or cloth may be stained with the ink leaked out when the user opens the cartridge package.
Also, it is thought that the cartridge package is opened under an atmospheric pressure as low as 0.7 in some cases depending on the altitude of the place where the user employs an ink jet cartridge. Under such a low atmospheric pressure, the ink may also leak to the outside of the ink jet cartridge as with the foregoing case.
To prevent the leakage of ink in those situations, a buffer chamber is generally provided between the atmosphere communicating port 23 and the ink absorbing member 21, making it hard for the ink leaked out of the ink absorbing member 21 to exude to the outside of the ink jet cartridge. However, the volume of the buffer chamber is so very small that the function of the buffer chamber is not always developed satisfactorily.
Further, if the ink is impregnated in a portion of the ink absorbing member 21 which enters the buffer chamber, the guide paths formed by the ribs for distributing the ambient air introduced through the atmosphere communicating port 23 to various portions of the ink absorbing member are blocked off. This raises the problem that the ink impregnated in the ink absorbing member is no longer uniformly supplied to the recording head 27.
The present invention has been accomplished in view of the above-stated problems in the prior art, and its object is to provide an ink jet cartridge which can prevent an ink absorbing member from entering a buffer chamber and which can uniformly supply ink impregnated in the ink absorbing member to a recording head.
Another object of the present invention is to provide an ink jet cartridge which can prevent ink from leaking to the outside even if the cartridge is subjected to a thermal impact or a pressure reduced state.
To achieve the above objects, the present invention provides an ink tank for storing ink supplied to an ink jet recording head, the ink tank comprising an ink tank body, an ink absorbing member inserted in the ink -tank body in a compressed state, an atmosphere communicating port for communicating an inner space of the ink tank body with the atmosphere, and an ink supply port coupled to the ink jet recording head and serving as an ink supply port, wherein a corner of the ink absorbing member which would be located near the atmosphere communicating port is cut out, a portion of the ink absorbing member around the cutout area is partly released in a degree of compression as compared with the other portion thereof under the state where the ink absorbing member is inserted in the ink tank body in a compressed state, and a space area is formed between the cutout area of the ink absorbing member and the atmosphere communicating port.
With the present invention constituted as set forth above, a corner of the ink absorbing member which would be located adjacent to a buffer chamber when the ink absorbing member is inserted in the ink tank, is cut out so that any part of the ink absorbing member will not enter the buffer chamber. Therefore, even if the ink absorbing member is pushed toward the buffer chamber when it is inserted in the ink tank while being compressed, the ink absorbing member can be surely prevented from entering the buffer chamber. Additionally, guide paths formed for supplying the ambient air introduced through the atmosphere communicating port to the ink absorbing member will not be blocked off.
Also, the ink absorbing member is configured such that when it is inserted in the ink tank, a space of which volume is at least 0.5 time the volume of a vacant space in the ink absorbing member where the ink is not impregnated, is left near the atmosphere communicating port. Therefore, even if the air contained in the ink absorbing member expands due to, e.g., a pressure reduction outside the ink tank and the ink is forced to leak out of the ink absorbing member corresponding the expansion of the air, the leaked ink is accommodated in the above space formed when the ink absorbing member is inserted in the ink tank, and the ink is surely prevented from leaking to the outside of the ink jet cartridge.
Further, a corner of the ink absorbing member is cut out so that the ink absorbing member will not contact a rib on the tank inner wall surface over a predetermined length near the atmosphere communicating port. Therefore, when the ink absorbing member is inserted in the ink tank in a compressed state, a portion of the ink absorbing member near the atmosphere communicating port is not compressed and no ink will be accumulated near the atmosphere communicating port.